CN114200571B - Optical waveguide and head-mounted device with two super-surface gratings - Google Patents
Optical waveguide and head-mounted device with two super-surface gratings Download PDFInfo
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- CN114200571B CN114200571B CN202210135369.8A CN202210135369A CN114200571B CN 114200571 B CN114200571 B CN 114200571B CN 202210135369 A CN202210135369 A CN 202210135369A CN 114200571 B CN114200571 B CN 114200571B
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
- G02B6/0013—Means for improving the coupling-in of light from the light source into the light guide
- G02B6/0015—Means for improving the coupling-in of light from the light source into the light guide provided on the surface of the light guide or in the bulk of it
- G02B6/0016—Grooves, prisms, gratings, scattering particles or rough surfaces
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/01—Head-up displays
- G02B27/017—Head mounted
- G02B27/0172—Head mounted characterised by optical features
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
- G02B6/0033—Means for improving the coupling-out of light from the light guide
- G02B6/005—Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
- G02B6/124—Geodesic lenses or integrated gratings
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Abstract
The invention provides an optical waveguide with two super surface gratings and a head-mounted device. Wherein, the optical waveguide comprises an optical waveguide sheet, and first and second super-surface gratings with different structures; the first super surface grating comprises three strip-shaped units with the same height and width; the three strip-shaped units are arranged in parallel at a first distance to form a basic unit, and the basic unit is periodically arranged on the surface of the optical waveguide sheet at a second distance; under the condition that the height of the strip-shaped unit is more than or equal to one third of the minimum wavelength of the light beam emitted by the optical machine, the light beam enters the first super-surface grating to be deflected for the first time and generate a phase difference which is in direct proportion to the height of the strip-shaped unit, enters the optical waveguide sheet to be deflected for the second time to two sides and to be totally reflected, and is respectively emitted from the two second super-surface gratings to be imaged in human eyes, and the second super-surface gratings only deflect the light beam in a single direction. The invention can realize bidirectional pupil expansion towards two sides through the first super-surface grating, thereby improving the utilization rate of the optical waveguide.
Description
Technical Field
The invention relates to the technical field of super surfaces, in particular to an optical waveguide and a head-mounted device with two super surface gratings.
Background
Augmented Reality (AR) forms a true and unreal display effect by projecting a virtual image to human eyes and superimposing the virtual image with a real space. The augmented reality provides unprecedented experience for users by means of human-computer interactivity, realistic immersion and rich imagination space, and has very wide application prospects in the fields of industry, consumer electronics and the like. The implementation of augmented reality display devices is typically either a traditional geometrical optical lens based solution or an optical waveguide based solution.
The optical waveguide is a technology for realizing near-to-eye image display by utilizing a grating, and the optical element is turned to a plane from a stereo state from a millimeter level to a micro-nanometer level, so that the application of the optical waveguide in AR equipment is promoted. The optical waveguide can conduct the image to human eyes through total reflection compression, has characteristics frivolous, that the transmissivity is high, and the outward appearance is close near-sighted lens, relatively accords with the demand of consumer-grade AR equipment.
Currently, the leading microsoft HoloLens in the AR industry is to form a color picture by stacking 2 to 3 optical waveguides to realize three-color mixing, wherein each optical waveguide adopts a surface relief grating for light coupling and light outcoupling. The problems of dispersion, ghost and the like are easily caused when a plurality of optical waveguide sheets are superposed and used, and the problems of image leakage and dizziness caused by binocular parallax due to the fact that a projection part of the optical waveguide sheets is large in size and multi-level diffraction exists.
Disclosure of Invention
The invention provides an optical waveguide with two super-surface gratings and a head-mounted device, which are used for solving the problems that the optical waveguide is easy to generate dispersion, ghost and the like in the prior art and the problems of image leakage caused by multi-level diffraction and dizziness caused by binocular parallax.
In a first aspect, the present invention provides an optical waveguide with two types of super surface gratings, comprising: an optical waveguide sheet, a first super-surface grating and two second super-surface gratings; the first super-surface grating is arranged in the middle area on the surface of the optical waveguide sheet close to the optical machine, and the two second super-surface gratings are respectively arranged in the left side area and the right side area on the surface of the optical waveguide sheet close to the human eyes;
the first super surface grating and the second super surface grating have different structures, and the first super surface grating includes: the first strip-shaped unit, the second strip-shaped unit and the third strip-shaped unit have the same height and width, and the width of the strip-shaped unit is smaller than that of the strip-shaped unit; the first strip-shaped units and the second strip-shaped units, and the second strip-shaped units and the third strip-shaped units are respectively separated by a first distance and are arranged on the surface of the optical waveguide sheet in parallel to form basic units of the first super-surface grating, and the basic units are periodically arranged on the surface of the optical waveguide sheet by a second distance;
under the condition that the height of the strip-shaped unit is more than or equal to one third of the minimum wavelength of the light beam emitted by the optical machine, the light beam emitted by the optical machine enters the first super-surface grating, is subjected to primary deflection through the basic unit, is accumulated to generate a phase difference with the height of the strip-shaped unit in a proportional manner, enters the optical waveguide sheet to be subjected to secondary deflection towards two sides, is subjected to total reflection in the optical waveguide sheet respectively, and is emitted from the two second super-surface gratings to be imaged by human eyes respectively, wherein the second super-surface grating only performs one-way deflection on the light beam, and the coupling of the light beam among the three strip-shaped units in the basic unit can be ignored.
According to the optical waveguide with two types of super surface gratings, the first super surface grating and the second super surface grating are arranged on the surface of the same side of the optical waveguide sheet; alternatively, the first and second electrodes may be,
the first super surface grating and the second super surface grating are disposed on surfaces of opposite sides of the optical waveguide sheet.
According to the optical waveguide with two types of super-surface gratings provided by the present invention, the second super-surface grating includes: a fourth strip unit and a fifth strip unit, wherein the fourth strip unit and the fifth strip unit have the same height, and the width of the fourth strip unit is smaller than the width of the fifth strip unit and smaller than the height of the strip unit;
the fourth strip-shaped elements are arranged on the surface of the optical waveguide sheet in parallel at a third distance from the fifth strip-shaped elements, constitute basic elements of the second super-surface grating, and are periodically arranged on the surface of the optical waveguide sheet at a fourth distance.
According to the optical waveguide provided by the invention, the phase difference is constant according to the two super surface gratings
The wavelength of the light beam, theDetermining the height of the strip-shaped units and the effective refractive index among the strip-shaped units in the basic unit;
the sine value of a deflection angle generated by the accumulation of the two deflections is determined according to the wavelength of the light beam, the refractive index of the optical waveguide sheet and the second distance of the first super-surface grating;
first distance of the first super surface grating is constant
The phase difference, the wavelength of the light beam, and the sine of the deflection angle.
According to the optical waveguide with two types of super surface gratings, the first strip-shaped unit, the second strip-shaped unit and the third strip-shaped unit are made of the same material, and the material comprises one of silicon oxide, silicon nitride, gallium nitride and titanium dioxide; and/or the presence of a gas in the gas,
the fourth strip units and the fifth strip units are made of the same material, and the material comprises one of silicon oxide, silicon nitride, gallium nitride and titanium dioxide.
According to the optical waveguide with two types of super-surface gratings, provided by the invention, the material of the optical waveguide sheet is fused quartz.
According to the optical waveguide with two types of super-surface gratings provided by the invention, the first super-surface grating and the second super-surface grating are manufactured by using the optical waveguide sheet as a substrate and adopting a semiconductor manufacturing process.
According to the optical waveguide with two types of super surface gratings, the first strip-shaped unit, the second strip-shaped unit, the third strip-shaped unit, the fourth strip-shaped unit and the fifth strip-shaped unit are made of titanium dioxide;
the heights of the first strip-shaped unit, the second strip-shaped unit, the third strip-shaped unit, the fourth strip-shaped unit and the fifth strip-shaped unit are 150-450 nm, the widths of the first strip-shaped unit, the second strip-shaped unit and the third strip-shaped unit are 20-150 nm, the width of the fourth strip-shaped unit is 20-100 nm, and the width of the fifth strip-shaped unit is 60-200 nm;
the first distance and the third distance are 100-300 nm, the second distance and the fourth distance are 400-1000 nm, and the refractive index of the optical waveguide sheet is 1.4-2.2.
In a second aspect, the invention provides a head-mounted device comprising a lens made of the optical waveguide with two types of super-surface gratings described in the first aspect.
The head-mounted equipment provided by the invention comprises one of augmented reality glasses and an augmented reality helmet.
The invention provides an optical waveguide and a head-mounted device with two super-surface gratings, wherein the super-surface gratings are used as an incoupling grating and an outcoupling grating in the optical waveguide, so that the effective spectral range of the existing monolithic grating can be expanded from 465nm to 615nm, and the monolithic optical waveguide realizes color display and solves the problems of dispersion, ghost shadow and the like; the coupled grating only keeps positive and negative first-order diffraction light to expand the pupil at two sides, so that the utilization rate of the optical waveguide can be improved; the single-side diffraction efficiency can reach more than 40%, the total first-order diffraction efficiency can reach more than 80%, the multi-level diffraction can be effectively inhibited, the problems of image leakage and dizziness caused by binocular parallax are solved, and a better imaging effect can be obtained; meanwhile, the thin film type super-surface grating is light, thin and small in size, and can reduce the power consumption of components as an incoupling grating, so that the optical efficiency of the optical waveguide is improved; the field angle can be enlarged by adjusting the refractive index of the optical waveguide sheet, so that the field angle can reach 50 degrees; the light-coupling grating can keep higher reflection efficiency and is convenient for pupil expansion; the two-dimensional pupil expansion can be realized through the combination of the coupling-in grating and the coupling-out grating; the requirements of the AR equipment on lightness, smallness, privacy, high efficiency and long-time wearing can be met.
Drawings
In order to more clearly illustrate the technical solutions of the present invention or the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of the structure of an optical waveguide with two types of super-surface gratings according to the present invention;
FIG. 2 is a front view of a first supersurface grating in the optical waveguide of FIG. 1;
FIG. 3 is a top view of the first super-surface grating of FIG. 2;
FIG. 4 is a far field schematic of a first super-surface grating provided by the present invention;
FIG. 5 is a schematic diagram of a light beam entering a human eye for imaging through the optical waveguide of FIG. 1;
FIG. 6 is a front view of a second supersurface grating in the optical waveguide of FIG. 1;
FIG. 7 is a top view of the second super surface grating of FIG. 6;
FIG. 8 is a far field schematic of a second super-surface grating provided by the present invention;
FIG. 9 is a schematic phase shift diagram of an embodiment of a super-surface grating provided by the present invention;
FIG. 10 is a schematic representation of the diffraction efficiency of an embodiment of a first super-surface grating provided by the present invention;
FIG. 11 is a graphical representation of the diffraction efficiency of an embodiment of a second super-surface grating provided in accordance with the present invention;
fig. 12 is a schematic view showing a change in angle of view of the first super surface grating provided by the present invention with the refractive index of the optical waveguide sheet.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
The super surface is composed of sub-wavelength artificial structural units, has excellent physical properties which are not possessed by natural materials, and the characteristics of the super surface depend on the arrangement and combination mode of basic structural units and do not depend on the properties of basic unit materials. By reasonably designing the internal structure of the super surface, namely the arrangement mode of the basic units, the excellent material characteristics which natural materials do not have in nature can be realized, and the arbitrary control and transformation of visible light, microwave, sound wave and the like can be realized. Compared with the traditional refractive index material and the three-dimensional meta-material, the meta-surface has the geometrical characteristics of thinness and flatness, so that the meta-surface is easier to manufacture compared with the three-dimensional meta-material, has lower manufacturing cost and is easy to further integrate with other components. These unique and superior properties make the super-surface an excellent planar element for manipulating light. The super-surface element can be further integrated with other components, so that a multifunctional high-density large-scale device is realized. The use of super-surface gratings as coupling gratings in optical waveguides has become one of the main development directions in the field of near-eye display optics.
The present invention provides an optical waveguide using two types of super-surface gratings as an incoupling grating and an outcoupling grating in the optical waveguide, respectively, please refer to fig. 1, fig. 2, fig. 3, fig. 4 and fig. 5, fig. 1 is a schematic diagram of the composition structure of the optical waveguide having two types of super-surface gratings provided by the present invention; FIG. 2 is a front view of a first supersurface grating in the optical waveguide of FIG. 1; FIG. 3 is a top view of the first super-surface grating of FIG. 2; FIG. 4 is a far field schematic of a first super-surface grating provided by the present invention; fig. 5 is a schematic diagram of a light beam entering the human eye to be imaged through the optical waveguide in fig. 1.
As shown in fig. 1, an optical waveguide having two types of super surface gratings includes: an optical waveguide sheet 110, a first super-surface grating 120, and two second super-surface gratings 130 and 140; the first super-surface grating 120 is disposed in the middle region on the surface of the optical waveguide sheet 110 on the side close to the optical device, and serves as a coupling-in grating of the optical waveguide. Two second super-surface gratings 130 and 140 are respectively disposed in left and right side regions on the surface of the optical waveguide sheet 110 on the side close to the human eye, as coupling-out gratings of the optical waveguide. As shown in fig. 2 and 3, the first super surface grating 120 includes: first, second, and third stripe units 121, 122, and 123, the first stripe unit 121, the second stripe unit 122, and the third stripe unit 123 may be micro-nano structures with rectangular cross sections and have the same heightL 1 And widthW 1 And the width of the stripe units 121, 122 and 123W 1 Is smaller than the height of the stripe units 121, 122 and 123L 1 . The first stripe units 121 and the second stripe units 122, and the second stripe units 122 and the third stripe units 123 are respectively spaced apart by a first distanceD 1 Arranged in parallel on the surface of the optical waveguide sheet 110, constituting a basic unit of the first super-surface grating 120, the basic unit being at a second distance
Periodically disposed on the surface of the optical waveguide sheet 110. Wherein, heightL 1 、Width ofW 1 A first distanceD 1 And a second distance
All the measurement units of (A) are nanometers. The second supersurface gratings 130 and 140 may have different structures from the first supersurface grating 120, and the structure of the second supersurface gratings 130 and 140 is not limited by the embodiment of the present invention.
In some alternative examples, the second supersurface gratings 130 and 140 may use the same principles as the first supersurface grating 120. For example, as shown in fig. 6, 7 and 8, the second super-surface gratings 130 and 140 may include: a fourth strip unit 131 and a fifth strip unit 141, the fourth strip unit 131 and the fifth strip unit 141 having the same heightL 2 Width of fourth stripe cell 131W L May be smaller than the fifth bar element 141W R And is smaller than the height of the stripe units 131 and 141L 2 The fourth strip unit 131 is spaced from the fifth strip unit 141 by a third distanceD 2 Arranged in parallel on the surface of the optical waveguide sheet 110, constituting the basic unit of the second super-surface gratings 130 and 140, at a fourth distance
Periodically disposed on the surface of the optical waveguide sheet 110.
As shown in fig. 4 and 5, at the height of the bar units 121, 122 and 123L 1 In case of sufficient height, for example, greater than or equal to one third of the minimum wavelength of the light beam emitted by the optical engine, the light beam emitted by the optical engine is incident on the first super-surface grating 120, is deflected for the first time by the basic unit, and cumulatively generates the height of the bar-shaped units 121, 122 and 123L 1 And the light beams deflected to both sides are totally reflected in the optical waveguide sheet 110 and exit from the two second super-surface gratings 130 and 140 respectively, and enter human eyes to form images on the human eyes, wherein the second super-surface gratings 130 and 140 only deflect the light beams in a single direction, and the coupling of the light beams among the three strip units 121, 122 and 123 in the basic unit can be ignored.
In the present embodiment, the first super surface grating 120 uses a generalized snell's law, which implements the principle of beam coupling, unlike the surface relief grating using the diffraction principle: when the heights of the first stripe unit 121, the second stripe unit 122 and the third stripe unit 123 are higherL 1 When the height is high enough, the light beam emitted by the optical engine enters the first super surface grating 120 from the air, the light beam with the approximate fundamental mode is transmitted in the waveguide, the phase and the transmittance of the light beam are determined by the transmission characteristics of the light with the fundamental mode of the waveguide, and the transmission characteristics of the light with the fundamental mode of the waveguide are determined by the refractive indexes of the first strip units 121, the second strip units 122 and the third strip units 123 and the width of the optical waveguide sheet 110. By arranging the first stripe unit 121, the second stripe unit 122, and the third stripe unit 123 side by side in the first super surface grating 120, optical coupling between the stripe units is negligible, and a phase shift accumulated by a light beam moving along the stripe units
I.e. phase difference, and heightL 1 Is proportional, wherein the phase difference
And heightL 1 The relationship between them can be expressed by equation 1, which is of the form:
wherein, the first and the second end of the pipe are connected with each other,
wavelength of the light beam
The effective refractive index between the first stripe units 121, the second stripe units 122 and the third stripe units 123 can be adjusted by adjusting the widths of the first stripe units 121, the second stripe units 122 and the third stripe units 123W 1 To make the effective refractive index of the base film light
The effective refractive index can be directly measured and obtained by using measurement software in practical application from the change of the refractive index of light in air to the change of the refractive index of light in the strip-shaped unit material
。
The angle of deflection of the light beam through the first stripe unit 121, the second stripe unit 122 and the third stripe unit 123 of the first super surface grating 120
Can be expressed by equation 2, equation 2 is of the form:
considering that the light beam enters the optical waveguide sheet 110 to be deflected, the angle at which the light beam enters the optical waveguide sheet 110 to be deflected for the second time
Can be expressed by equation 4, equation 4 is of the form:
wherein the content of the first and second substances,
which is the refractive index of the optical waveguide sheet 110,
the period of the elementary cells in the first supersurface grating 120, i.e. the second distance. Thus, the device，The light beam passes through the first super-surface grating 120 and the optical waveguide sheet 110, and is deflected twice to form a deflection angle
Can be expressed by equation 5, equation 5 is of the form:
after the deflection angle has been determined
Phase difference of sum
Then, the first distance in the first super surface grating 120 can be obtained according to equation 6D 1 Equation 6 is of the form:
from the above formula, it can be seen that: the phase difference generated by the light beam passing through the first super surface grating 120
Can be based on constants
Wavelength of light beam
Heights of the first, second, and third stripe units 121, 122, and 123L 1 And effective refractive indexes among the first stripe units 121, the second stripe units 122, and the third stripe units 123
(ii) a Or (c). Deflection angle generated by accumulation of two deflections
The sine value of (2) can be based on the wavelength of the light beam
Refractive index of the optical waveguide sheet 110
And a second distance of the first super surface grating 120
And (5) determining. First distance of the first super surface grating 120D 1 Can be based on a constant
Phase difference of
Wavelength of the light beam
And angle of deflection
The sine value of (c) is determined. Therefore, the height can be reasonably setL 1 And a second distance
Or by reasonably setting the first distanceD 1 And a second distance
Obtaining a value satisfying the phase difference
Angle of deflection
The desired first super-surface grating 120.
When the second super surface gratings 130 and 140 use the same principle as the first super surface grating 120, the phase difference generated by the light beam passing through the second super surface gratings 130 and 140
Can be based on constants
Wavelength of light beam
Height of fourth strip element 131 and fifth strip element 141L 2 And an effective fold between the fourth strip unit 131 and the fifth strip unit 141
Refractive index
(ii) a Or (b) to (c). Deflection angle generated by accumulation of two deflections
Can be based on the wavelength of the light beam
Refractive index of the optical waveguide sheet 110
And a fourth distance of the second super surface gratings 130 and 140
And (4) determining. Third distance of the second super-surface gratings 130 and 140D 2 Can be based on a constant
Phase difference of
Wavelength of light beam
And angle of deflection
The sine value of (c) is determined. FIG. 9 is a schematic diagram of phase shift of an embodiment of a super surface grating provided by the present invention, as shown in FIG. 9, wherein the beam generates 0.5 after passing through two stripe units 131 and 141
A phase difference, and a dotted line indicates a direction in which the light beam is first deflected after passing through the two stripe units 131 and 141, and may indicate an angle of the first deflection
. Therefore, the height can be reasonably setL 2 And a fourth distance
Or by reasonably setting the third distanceD 2 And a fourth distance
Obtaining a value satisfying the phase difference
Angle of deflection
The required second super-surface gratings 130 and 140.
In the embodiment of the present invention, the first stripe units 121, the second stripe units 122, and the third stripe units 123 in the first super-surface grating 120 may be made of the same material, and the first stripe units 121, the second stripe units 122, and the third stripe units 123 may be made of a material having high transmittance in a visible light band, for example, one of silicon oxide, silicon nitride, gallium nitride, titanium dioxide, and the like, which is not limited in the embodiment of the present invention. The material of the optical waveguide sheet 110 may be fused silica. Alternatively, the fourth stripe units 131 and the fifth stripe units 141 in the second super surface gratings 130 and 140 may be made of the same material, and the fourth stripe units 131 and the fifth stripe units 141 may be made of a material having high transmittance in the visible light band, for example, one of silicon oxide, silicon nitride, gallium nitride, titanium dioxide, and the like may be used, which is not limited in the embodiment of the present invention. The first and second super-surface gratings 120 and 130 and 140 may be fabricated by using the optical waveguide sheet 110 as a substrate and using a semiconductor fabrication process to meet requirements of high volume production and high precision, for example, the semiconductor fabrication process may include processes of glue coating, exposure, atomic layer deposition, etching, glue removal, and the like.
In some optional examples, the first super surface lightThe first stripe units 121, the second stripe units 122, and the third stripe units 123 in the grating 120, and the fourth stripe units 131 and the fifth stripe units 141 in the second super surface gratings 130 and 140 may employ titanium dioxide. Wherein, the heights of the first stripe unit 121, the second stripe unit 122 and the third stripe unit 123L 1 Can be 150-450 nm in widthW 1 Can be 20-150 nm, the first distanceD 1 Can be 100-300 nm, the second distance
Can be 400-1000 nm. Height of fourth strip unit 131 and fifth strip unit 141L 2 Can be 150-450 nm, and the width of the fourth strip-shaped unit 131W L Can be 20-100 nm, and the width of the fifth strip-shaped unit 141W R Can be 60-200 nm, third distanceD 2 Can be 100-300 nm, fourth distance
Can be 400-1000 nm. The refractive index of the optical waveguide sheet 110 may be 1.4 to 2.2.
Optionally, when the optical waveguide with two types of super-surface gratings provided in the embodiment of the present invention is applied to a head-mounted device, the light beam emitted by the optical engine 200 may be a light beam carrying image information, the light beam carrying image information is incident to the first super-surface grating 120, and a phase difference is generated by the first super-surface grating 120
To generate a phase difference
The light beam entering the optical waveguide sheet 110 is angled to both sides
Is deflected to both sides by an angle of
The deflected light beams of (2) are totally reflected in the optical waveguide sheet 110, respectively, and exit from the second super surface gratings 130 and 140, respectively, to enter human eyes, forming a virtual image in the human eyes.
In some alternative examples, the first super-surface grating 120 and the two second super-surface gratings 130 and 140 are disposed on the same side surface of the optical waveguide sheet 110. In other alternative examples, the first super-surface grating 120 and the two second super-surface gratings 130 and 140 are disposed on the surfaces of the optical waveguide sheet 110 on opposite sides. The first super-surface grating 120 and the two second super-surface gratings 130 and 140 are disposed on the surface of the same side of the optical waveguide sheet 110, and the first super-surface grating 120 and the two second super-surface gratings 130 and 140 are disposed on the surfaces of the opposite sides of the optical waveguide sheet 110, and the process and principle of light beam propagation are the same, so that the details are not described herein.
Referring to fig. 10, fig. 10 is a schematic diagram illustrating diffraction efficiency of an embodiment of a first super-surface grating provided in the present invention. As shown in FIG. 10, T 1 For positive first diffraction order, T -1 Is the negative first order diffraction, T is the total diffraction, and R is the reflectivity. It can be seen that the structure of the first super-surface grating 120 provided by the present invention can suppress zero-order diffraction and high-order diffraction, only first-order diffraction is retained, the positive and negative first-order diffraction efficiencies in the spectral range of 465nm to 615nm are 40% respectively, the total first-order diffraction efficiency can reach 80%, and a broad band and high efficiency can be achieved.
Referring to fig. 11, fig. 11 is a schematic diagram of diffraction efficiency of a second super-surface grating according to an embodiment of the present invention. As shown in fig. 11, for the light guide, the higher the diffraction efficiency of the incoupling grating, the better, and the outcoupled grating can have the appropriate diffraction efficiency by adjusting the structural parameters of the second super-surface gratings 130 and 140 in order to have enough reflected light to continue to participate in the pupil expansion process.
Referring to fig. 12, fig. 12 is a schematic view illustrating that a viewing angle of the first super surface grating varies with a refractive index of the optical waveguide sheet according to the present invention. As shown in fig. 12, the angle of view can be affected by changing the refractive index of the optical waveguide sheet 110 in the optical waveguide, and when the optical waveguide sheet 110 uses fused silica having a refractive index of 1.5, the angle of view of the first super surface grating 122 in the optical waveguide is 30 °, and the angle of view of the first super surface grating 120 in the optical waveguide can be expanded to about 50 ° as the refractive index of the optical waveguide sheet 110 increases.
In the two optical waveguides of the super-surface grating provided by the embodiment of the invention, the super-surface grating is used as the coupling grating and the coupling grating in the optical waveguide, so that the effective spectral range of the existing monolithic grating can be expanded from 465nm to 615nm, color display is realized through the monolithic optical waveguide, and the problems of dispersion, ghost and the like are solved; the coupled grating only keeps positive and negative first-order diffraction light to expand the pupil at two sides, so that the utilization rate of the optical waveguide can be improved; the single-side diffraction efficiency can reach more than 40%, the total first-order diffraction efficiency can reach more than 80%, the multi-level diffraction can be effectively inhibited, the problems of image leakage and dizziness caused by binocular parallax are solved, and a better imaging effect can be obtained; meanwhile, the thin film type super-surface grating is light, thin and small in size, and can reduce the power consumption of components as an incoupling grating, so that the optical efficiency of the optical waveguide is improved; the field angle can be enlarged by adjusting the refractive index of the optical waveguide sheet, so that the field angle can reach 50 degrees; the light-coupling grating can keep higher reflection efficiency and is convenient for pupil expansion; the two-dimensional pupil expansion can be realized through the combination of the coupling-in grating and the coupling-out grating; the requirements of the AR equipment on lightness, compactness, high efficiency and long-time wearing can be met.
The invention also provides a head-mounted device which comprises the lens manufactured by the optical waveguide with the two super-surface gratings in any embodiment. The first super-surface grating 120 may be located at the center of the forehead of the human body, and is configured to receive a light beam carrying image information and sent by the optical engine 200; the second super-surface grating 130 may be located at the left eye, and the second super-surface grating 140 may be located at the right eye, for receiving the light beam carrying the image information emitted from the optical waveguide sheet 110. Wherein, the light beam carrying the image information enters the first super surface grating 120, generates a phase difference through the first super surface grating 120, the light beam generating the phase difference enters the optical waveguide sheet 110 to be deflected to both sides, the light beam deflected to both sides is totally reflected in the optical waveguide sheet 110, the light beam totally reflected is emitted out from the second super surface grating 130 and 140, enters the human eye, and forms a virtual image at the human eye.
Optionally, the head-mounted device may include one of augmented reality glasses and an augmented reality helmet. Augmented reality glasses and augmented reality helmets are often used in the medical field, commercial activities, and the movie field, etc.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (9)
1. An optical waveguide having two types of supersurface gratings, comprising: an optical waveguide sheet, a first super-surface grating and two second super-surface gratings; the first super-surface grating is arranged in the middle area on the surface of the optical waveguide sheet close to the optical machine, and the two second super-surface gratings are respectively arranged in the left side area and the right side area on the surface of the optical waveguide sheet close to the human eyes;
the first and second super-surface gratings have different structures, and the first super-surface grating includes: the first strip-shaped unit, the second strip-shaped unit and the third strip-shaped unit have the same height and width, and the width of the strip-shaped unit is smaller than that of the strip-shaped unit; the first strip-shaped units and the second strip-shaped units, and the second strip-shaped units and the third strip-shaped units are respectively arranged on the surface of the optical waveguide sheet in parallel at a first distance to form basic units of the first super-surface grating, and the basic units are periodically arranged on the surface of the optical waveguide sheet at a second distance;
under the condition that the height of the strip-shaped unit is more than or equal to one third of the minimum wavelength of the light beam emitted by the optical machine, the light beam emitted by the optical machine enters the first super-surface grating, is subjected to primary deflection through the basic unit, cumulatively generates a phase difference proportional to the height of the strip-shaped unit, enters the optical waveguide sheet to be subjected to secondary deflection towards two sides, is subjected to total reflection in the optical waveguide sheet respectively, and is emitted from the two second super-surface gratings to be imaged on human eyes respectively, wherein the second super-surface grating only performs unidirectional deflection on the light beam, and the coupling of the light beam among the three strip-shaped units in the basic unit can be ignored;
said phase difference is dependent on a constant
Determining the wavelength of the light beam, the height of the strip-shaped units and the effective refractive index between the strip-shaped units in the basic unit, and phase difference
Comprises the following steps:
wherein the content of the first and second substances,
is the wavelength of the light beam
Is the effective refractive index among the first strip-shaped unit, the second strip-shaped unit and the third strip-shaped unit,
the height of the strip-shaped unit;
the sine value of the deflection angle generated by the accumulation of the two deflections is determined according to the wavelength of the light beam and the sine value of the deflection angleThe refractive index of the optical waveguide sheet and the second distance of the first super surface grating are determined, and the deflection angle generated by the accumulation of two deflections
The sine value of (c) is:
wherein, the first and the second end of the pipe are connected with each other,
is a refractive index of the optical waveguide sheet,
the period of the basic unit in the first super surface grating is the second distance;
the first distance of the first super-surface grating is constant
The phase difference, the wavelength of the light beam and the sine of the deflection angle, a first distance in the first super surface gratingDComprises the following steps:
2. the optical waveguide having two types of super surface gratings according to claim 1, wherein the first super surface grating and the second super surface grating are provided on a surface of the optical waveguide sheet on the same side; alternatively, the first and second liquid crystal display panels may be,
the first super surface grating and the second super surface grating are disposed on surfaces of opposite sides of the optical waveguide sheet.
3. The optical waveguide with two types of super surface gratings according to claim 1 or 2, wherein the second super surface grating includes: a fourth strip unit and a fifth strip unit, wherein the fourth strip unit and the fifth strip unit have the same height, and the width of the fourth strip unit is smaller than the width of the fifth strip unit and smaller than the height of the strip unit; the fourth strip-shaped elements are arranged on the surface of the optical waveguide sheet in parallel at a third distance from the fifth strip-shaped elements, constitute basic elements of the second super-surface grating, and are periodically arranged on the surface of the optical waveguide sheet at a fourth distance.
4. The optical waveguide with two types of super surface gratings according to claim 3, wherein the first strip-shaped unit, the second strip-shaped unit and the third strip-shaped unit are made of the same material, and the material comprises one of silicon oxide, silicon nitride, gallium nitride and titanium dioxide; and/or the presence of a gas in the atmosphere,
the fourth strip units and the fifth strip units are made of the same material, and the material comprises one of silicon oxide, silicon nitride, gallium nitride and titanium dioxide.
5. The optical waveguide with two types of super surface gratings according to claim 4, wherein the material of the optical waveguide sheet is fused silica.
6. The optical waveguide having two types of super-surface gratings according to claim 5, wherein the first super-surface grating and the second super-surface grating are manufactured by a semiconductor manufacturing process using the optical waveguide sheet as a substrate.
7. The optical waveguide with two types of super surface gratings according to claim 6, wherein the material of the first strip unit, the second strip unit, the third strip unit, the fourth strip unit and the fifth strip unit is titanium dioxide;
the heights of the first strip-shaped unit, the second strip-shaped unit, the third strip-shaped unit, the fourth strip-shaped unit and the fifth strip-shaped unit are 150-450 nm, the widths of the first strip-shaped unit, the second strip-shaped unit and the third strip-shaped unit are 20-150 nm, the width of the fourth strip-shaped unit is 20-100 nm, and the width of the fifth strip-shaped unit is 60-200 nm;
the first distance and the third distance are 100-300 nm, the second distance and the fourth distance are 400-1000 nm, and the refractive index of the optical waveguide sheet is 1.4-2.2.
8. Head-mounted device characterized by comprising a lens made of an optical waveguide with two types of super-surface gratings according to any one of claims 1 to 7.
9. The head-mounted device of claim 8, comprising one of augmented reality glasses and an augmented reality helmet.
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| CN108828717A (en) * | 2018-06-08 | 2018-11-16 | 武汉大学 | Optical path one-way conduction component structure and its application based on super surface balzed grating, |
| CN112444968A (en) * | 2019-08-29 | 2021-03-05 | 华为技术有限公司 | Augmented reality's optics superimposer and relevant equipment |
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| CN108828717A (en) * | 2018-06-08 | 2018-11-16 | 武汉大学 | Optical path one-way conduction component structure and its application based on super surface balzed grating, |
| CN112444968A (en) * | 2019-08-29 | 2021-03-05 | 华为技术有限公司 | Augmented reality's optics superimposer and relevant equipment |
| CN112630966A (en) * | 2020-12-16 | 2021-04-09 | 浙江大学 | Super surface micro-nano structure monolithic full-color waveguide lens and AR display device |
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